Thread supply device for textile machines

Abstract

A thread supply device for a textile machine, which device includes a drum on which a thread is wound to form an intermediate thread storage, and from which the thread is withdrawn over one end of the drum for supply to the textile machine. A brake means is disposed adjacent the withdrawal end of the drum and acts on the unwinding thread for imposing a braking effect thereon. The braking means acts progressively on the unwinding thread as it moves peripherally relative to the drum for either increasing or decreasing the braking effect on the thread, depending upon the relative peripheral direction of movement of the thread.

What is claimed is: 
     
       1. A thread supply device for textile machines, comprising a drum on which the thread issuing from a supply bobbin can be wound tangentially and withdrawn over the end either by rotation of the drum or, in the case of a stationary drum, by means of a disc-shaped or ring-shaped winding element rotating adjacent a free front drum rim while forming at least one thread winding such that the thread is withdrawn over a removal edge of the drum in the case of a rotating drum and over a sliding edge of the winding element in the case of a stationary drum, and that a thread control element is provided which is arranged stationary adjacent the removal edge in the case of a rotating drum and which serves as a lateral stop for the unwinding thread opposite the direction of movement of the removal edge, and which is located on the winding element adjacent the sliding edge in the case of a stationary drum and which limits the peripheral velocity of the thread unwinding about the sliding edge to the peripheral speed thereof, characterized in that, in order to use the thread supply device in small jacquard machines, a brake means acting progressively on the unwinding thread in the peripheral directon of the same is disposed in front of the thread control element in the sense of the thread rotation about the removal or sliding edge during thread removal such that the braking effect is amplified as the thread approaches the thread control element and is decreased as the thread moves away from the thread control element. 
     
     
       2. A thread supply device according to claim 1, wherein the brake means has a constant braking effect over an operating angle section of the thread rotation, and wherein the brake means has first and second variable braking angle sections disposed on opposite sides of the operating angle section such that the braking effect (1) increases as the thread moves from the operating angle section toward the thread control element into the first braking angle section and (2) decreases as the thread moves from the operating angle section away from said thread control element into the second braking angle section. 
     
     
       3. A thread supply device according to claim 1, wherein the brake means is a curved guide part over which the unwinding thread passes and is deflected farther out of its path the closer it approaches the thread control element in the direction of thread rotation about the removal or sliding edge during thread removal. 
     
     
       4. A thread supply device according to claim 3, wherein the curved guide part is a loop-shaped wire bracket positioned adjacent the removal or sliding edge, through whose interior the unwinding thread passes. 
     
     
       5. A thread supply device according to claim 4, wherein the wire bracket has the shape of a closed loop and includes (1) a stop section extending radially relative to the normal or sliding edge, the stop section defining said thread control element, (2) a first brake section connected to the stop section and extending circumferentially therefrom contrary to the direction of thread rotation during thread removal and having a radial spacing relative to the removal or sliding edge which is reduced as the distance from the stop section increases, (3) an operating section with a constant radial spacing from the removal or sliding edge, (4) a second brake section with a radial spacing from the removal or sliding edge which decreases even further as the circumferential distance from the stop section increases, (5) a shut-off section extending externally of the removal or sliding edge, and (6) a connecting section between the shut-off and stop sections which is not contacted by the thread in any normally occurring operational phase. 
     
     
       6. In a thread supply device for a textile machine, comprising a cylindrical drum structure on which a thread issuing from a supply bobbin can be wound tangentially and from which the thread can be withdrawn over one end, a winding structure for causing the thread to be wound on the drum structue, one of said structure being rotatable relative to the other of said structures about the longitudinal axis of said drum structure, and a stop structure disposed adjacent said one end of the drum structure and fixedly related to said winding structure for limiting the relative peripheral velocity between the drum structure and the withdrawn thread as the latter is removed from the drum structure and tends to move peripherally relative to said one end of said drum structure, the improvement wherein braking means is fixedly related relative to said stop structure and coacts with the withdrawn thread as it is unwound from said drum structure for applying a braking effect thereto, said braking means including a first brake portion extending peripherally of the drum structure adjacent said one end thereof for imposing a progressively increased braking effect on the withdrawn thread as the latter moves peripherally relative to the drum structure in a direction toward the stop structure, and said braking means including a second brake portion extending peripherally of said one end of said drum structure for progressively imposing a decreased braking effect on the withdrawn thread as it moves peripherally relative to the drum structure in a direction away from the stop structure. 
     
     
       7. A thread supply device according to claim 6, wherein said braking means includes a central operating portion disposed circumferentially between said first and second brake portions, said central operating portion extending peripherally with respect to said drum structure through a preselected angle, said central operating portion applying a substantially constant braking effect on the withdrawn thread. 
     
     
       8. A thread supply device according to claim 7, wherein one of said brake portions extends circumferentially of said drum structure away from one end of said central operating portion, said one brake portion extending progressively radially outwardly as it projects circumferentially away from said operating portion, and the other brake portion extending circumferentially of said drum structure away from the other end of said central operating portion, said other brake portion progressively projecting radially inwardly as it projects circumferentially away from said central operating portion, and said central operating portion being of a substantially constant radius as defined about the axis of said drum structure. 
     
     
       9. A thread supply device according to claim 8, wherein said braking means and said stop structure together form a single endless loop positioned adjacent said one end of the drum structure for engaging the withdrawn thread and for controlling the peripheral displacement thereof relative to said drum structure.